Hemodynamic performance enhancement through asymptomatic diaphragm stimulation

ABSTRACT

An implantable system, and methodology, for improving a heart&#39;s hemodynamic performance featuring (a) bimodal electrodes placeable on the diaphragm, out of contact with the heart, possessing one mode for sensing cardiac electrical activity, and another for applying cardiac-cycle-synchronized, asymptomatic electrical stimulation to the diaphragm to trigger biphasic, diaphragmatic motion, (b) an accelerometer adjacent the electrodes for sensing both heart sounds, and stimulation-induced diaphragmatic motion, and (c) circuit structure, connected both to the electrodes and the accelerometer, operable, in predetermined timed relationships to the presences of valid V-events noted in one of sensed electrical and sensed mechanical, cardiac activity, to deliver diaphragmatic stimulation. The circuit structure includes accelerometer-linked computer structure for enabling selective review, for later operational modifications, of stimulation-produced diaphragmatic motions, and in a modified form, may additionally include timing-adjustment substructure capable of making adjustments in the mentioned timed relationships.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/950,774, filed Apr. 11, 2018, for “Hemodynamic PerformanceEnhancement Through Asymptomatic Diaphragm Stimulation,” which is acontinuation of U.S. patent application Ser. No. 15/612,690, filed Jun.2, 2017, for “Hemodynamic Performance Enhancement Through AsymptomaticDiaphragm Stimulation,” now U.S. Pat. No. 9,968,786 issued May 15, 2018,which is a continuation of U.S. patent application Ser. No. 15/273,643,filed Sep. 22, 2016, for “Hemodynamic Performance Enhancement ThroughAsymptomatic Diaphragm Stimulation,” now U.S. Pat. No. 9,694,185 issuedJul. 4, 2017, which is a divisional of U.S. patent application Ser. No.14/107,976, filed Dec. 16, 2013, for “Hemodynamic PerformanceEnhancement Through Asymptomatic Diaphragm Stimulation,” now U.S. Pat.No. 9,498,625 issued Nov. 22, 2016, which claims the benefit of andpriority to U.S. Provisional Patent Application Ser. No. 61/739,704,filed Dec. 19, 2012, for “Hemodynamic Performance Enhancement ThroughAsymptomatic Diaphragm Stimulation to the Diaphragm/Heart Interface”,the entire disclosures of which are incorporated herein by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention pertains to an implantable medical system, and toan associated methodology, employing, and managed by electrical circuitstructure, which features logic-including, internal-control circuitryreferred to herein as computer structure, or more simply as a computer,for enhancing hemodynamic performance in subjects with cardiac diseasethrough applying carefully timed, regular, per-cardiac-cycle,synchronized, asymptomatic, electrical pulsed stimulation to thediaphragm intended to induce short-term occurrences of biphasicdiaphragmatic motion. In particular, it relates to such a system andmethodology which, in relation to each such stimulation, and throughoperation of the included control circuitry (which forms part of what isreferred to as electrical circuit structure), monitors and recordsinformation regarding resulting, induced diaphragmatic-motion for laterreview, and to accommodate potential, telemetry-adjusted,systemic-performance adaptation to improve diaphragmatic stimulationcharacteristics so as to maximize the sought hemodynamic-performanceenhancement. The system preferably additionally permits, in a modifiedform, selective, remote-telemetry-implemented communication from outsidethe anatomy to allow for other kinds of system-behavioral adjustments,such as ones that relate to timing matters.

The term “hemodynamic performance” is used synonymously herein with theterms “cardiovascular performance” and “cardiac function”. The biphasicdiaphragmatic motion produced by electrical stimulation, in accordancewith practice of the invention, is what is called hereincaudal-followed-by-cranial motion of the diaphragm. The included“computer-structure” logic componentry, which may be hard-wired toperform its intended functions, or more preferably fully or partiallyprogrammable, as by telemetry, may also feature an appropriatemicroprocessor. It may also include, or be appropriately internallyassociated with, a suitable “state machine” for implementing variousimportant timing controls, as will be explained below.

Pulsed stimulation of the type just above mentioned, properlycharacterized and applied, triggers, in each case, a very short (only afew tens of milliseconds) pulse-like, biphasic(singular-caudal-followed-by-singular-cranial) motion of the diaphragm,and, relatedly also, a substantially following pumping-relevant motionof the left ventricle in the heart which rests on the diaphragm. Thisstimulation creates this motion-generating activity in a manner which,when properly and synchronously timed in relation to the onset ofleft-ventricular contraction, improves hemodynamic performance throughenhancing the important cardiac pumping functions of both (a) latediastolic filling, and (b) early systolic contraction.

Asymptomatic stimulation implemented in the practice of the presentinvention is also referred to herein as PIDS stimulation—the acronymPIDS standing for the phrase “pacing induced diaphragmatic stimulation”.The mentioned monitoring and recording for laterstimulation-characteristic review, and possible revision purposes, arelinked with systemically control-circuitry-performed comparing of actualinduced diaphragmatic-motion waveforms with a provided and internallystored reference waveform.

Of key importance in all featural expressions of the present invention,systemic and methodologic, are (1) that sensing of what is referred toherein as a valid electrical or mechanical V-event, and (2) thatrelated, sensing-based, ultimate applying of electrical stimulation tothe diaphragm, take place, with the system installed for use with asubject, from an implanted systemic disposition directly adjacent, andpreferably in contact with, a selected surface region in the subject'sdiaphragm. Preferably, but not necessarily, this selected surfaceregion, which may be either an inferior (preferred), or a superior,surface region in the diaphragm, and which may be chosen to be at manydifferent, diaphragmatic surface locations, is disposed left-lateralrelative to the subject's anatomy—and under all circumstances, out ofcontact with the heart.

A V-event, in either category (electrical or mechanical), is definedherein as being either the onset of left-ventricular contraction, or acardiac electrical or mechanical event having a predictably knownrelationship to such an onset. A valid electrical V-event is treated asbeing either the electrical R or Q wave, and a valid mechanical V-eventis treated as being the S1 heart sound. Cardiac-cycle-by-cardiac-cycle,synchronized, diaphragmatic stimulation is timed, selectively indifferent ways—anticipatory (early), or following (late)—in relation toper-cardiac-cycle, detected, valid V-events.

Of special importance in certain featural expressions of the presentinvention, systemic and methodologic, is the effective incorporation inthe proposed system and associated methodology of a focus, through theuse of a system-included accelerometer, preferably multi-axial incharacter, and even more preferably three-dimensional in nature, on themonitoring and recording of the mechanical waveform ofper-cardiac-cycle, mechanical diaphragmatic biphasic motion which isactually produced by applied, electrical diaphragmatic stimulation incomparison with a pre-set, diaphragmatic-motion reference waveform.Information regarding non-conformance of these two waveforms—computeracquired and recorded according to the invention—is important forperiodic system-performance review, and in this context, is very usefulto support the making, when desired, of appropriate, per-cardiac-cycle,electrical stimulation-character modifications to enhance suchperformance.

It should be noted that while different embodiments of the invention mayuse different-axial-sensitivity accelerometers, preferred in mostapplications is the inclusion and use of a three-dimensional, i.e.,three-axis, accelerometer. Accordingly, the preferred systemic andmethodologic invention descriptions presented herein below are describedin the context of employment of a three-dimensional accelerometer.

Two, principal, implantable systemic forms, or embodiments, of theinvention are proposed, one of which features, as an entirety—i.e., as asingularity—a self-contained, self-powered, singular capsuleconstruction, and the other of which features a distribution, alsoself-powered, of components organized into two arrangements ofcomponents separated by an interconnecting, cross-communication leadstructure.

Other forms of the invention, not pictured or discussed herein, anddiffering specifically from the two, just-mentioned currently principal,preferred forms, are recognized to be very suitably possible to addressdifferent implantation applications, wherein the various systemcomponents, described below for the two invention forms particularly setforth herein, become organized in different implantable ways.

Regarding systemic performance functionality in the context of thepresent invention disclosure, the same, basic invention methodology, interms of the important, end-result achieving ofhemodynamic/cardiovascular performance enhancement through triggeredpulses of biphasic motion introduced into the diaphragm (as aboveoutlined), is implemented in both of the specifically herein describedsystemic invention forms.

Stimulation-induced diaphragmatic movements, as just generally describedabove, are, in relation to normal respiration-motion frequency(typically about 0.2-0.3-Hz), and as mentioned, short-term, relativelyhigh-frequency (typically about 12-15-Hz), pulse-like motions. Thesequick motions are superimposed on the regular, and much lower frequency,diaphragmatic respiration movements. The initial, short-term caudalmovement effected by diaphragmatic stimulation pulls on the leftventricle, and if well timed, such stimulation-resulting “pulling”increases the atrial contribution to left-ventricular filling duringlate diastole (i.e., a so-called “atrial kick”) with a resultingsubsequent increase in stroke volume via the recognized, Frank-Starlingmechanism. The secondary, stimulation-induced movement of the diaphragmwhich is cranial, and which is also much faster than regulardiaphragmatic respiratory motion, causes the left ventricle to be“kicked” upwardly, and If this secondary movement occurs in the earlypart of systole, and prior to the closure of the mitral valve, itenhances cardiac function further by increasing the momentum ofventricular contraction.

Accordingly, in relation to achieving desired hemodynamic-enhancement,it is important to optimize the timing between the onset of ventricularcontraction and diaphragmatic stimulation so that the actual timing andimpact of the mentioned caudal and cranial components of motion as theyaffect cardiac function are maximized. Such maximizing issubject-specific, in relation, of course, to a given subject'sparticular cardiac structure (electrically and mechanically), andaccordingly, medically-determined, properly associated, subject-specifictiming requirements are initially “set into the system of theinvention”, as will be explained. When all operational parameters areproperly “put in place”, the present invention successfully accomplishesappreciable hemodynamic-performance optimization.

As mentioned above, two, fully implantable, and fully self-powered,principal embodiments of the system of the present invention arespecifically illustrated and described herein, one of which, as statedabove, is a single-unit, self-contained, capsule-form arrangement, andthe other of which has a distributed-component,communication-lead-line-interconnecting form.

According to one manner of describing generally the structural nature ofthe present invention, what is proposed is a system including (a)bi-modal (cardiac-electrical-activity sensing in one mode, and relateddiaphragmatic electrical stimulating in the other mode) electrodestructure operatively connectable to a selected surface region in asubject's diaphragm, and (b) monitoring and controlling circuitstructure which is connected to the electrode structure, and operable(1) to receive and process electrode-structure-sensed electrical cardiacactivity when the electrode structure, under the influence of thecircuit structure, is functioning in its sensing mode, and (2), based onsuch receiving and processing, to communicate to the diaphragm via theelectrode structure, when the latter is functioning, also under theinfluence of the circuit structure, in its stimulating mode, appropriatediaphragmatic stimulation.

In a more particular sense respecting this just-above-presented systemicexpression of the invention, (a) the selected, diaphragmatic surfaceregion is disposed (1) preferably, but not necessarily, at a locationwhich is lateral, and even more specifically left-lateral, within asubject's anatomy, and (2) in all instances out of contact with, thesubject's heart, and (b) the mentioned circuit structure includescomputer structure which specifically operates, relative to the circuitstructure's delivery of electrical stimulation through the electrodestructure, to control appropriately predetermined timed relationshipsrelative to noted presences, in received and monitored cardiac-cycleelectrical-activity information, of valid electrical V-events.Additionally, contemplated in the practice of the invention are two,different categories of such predetermined timed, or timing,relationships, one of which involves anticipation of a next-expected,valid, cardiac-cycle, electrical V-event, and the other of whichinvolves a following of the last-sensed, valid, cardiac-cycle,electrical V-event. These same, two categories of timing relationshipsare equally applicable to another form of the system of the invention,discussed below, which further includes an accelerometer (single orplural-axis), also referred to herein as a mechanical sensing structure,that is designed to detect heart sounds, and in particular S1 heartsounds, as valid mechanical V-events.

An augmented form (the “another form” of the invention mentionedimmediately above) of this just-presented description of the inventionis one in which the proposed system further includes specifically athree-dimensional accelerometer (called also a mechanical sensingstructure), (a) disposed adjacent, and operatively associated with, theelectrode structure for contact-associated disposition in amotion-sensing relationship with, and with respect to, the subject'sdiaphragm, (b) operatively connected to the mentioned circuit structure,and (c) constructed to be responsive to any motion produced in thesubject's diaphragm as a consequence of electrical diaphragmaticstimulation, and in relation to such responsiveness, to generate andcommunicate to the circuit structure a diaphragmatic-motion confirmationsignal possessing a waveform which is directly indicative of suchmotion.

In a further way of thinking about the accelerometer-including systemform of the invention, the circuit structure's included computerstructure features a waveform monitoring and recording substructure forcomparing the waveform of a communicated confirmation signal with areference waveform, and recording the conformation-signal waveform forsubsequent review.

Another way of thinking about the invention, in relation to theinclusion therein of an accelerometer, is that, in accordance with amodified form of the invention, (a) an included accelerometer functions,additionally, for sensing, in a subject's cardiac cycles, cardiac-cycle,S1 heart-sound, mechanical activity—a valid mechanical V-event—which isdiscernible at the selected, diaphragmatic surface region, and that (b),the included circuit structure receives this mechanical valid V-eventinformation from the accelerometer, and is operable, in predeterminedtimed relationships to noted presences, in such received mechanicalS1-heart-sound, of valid V-event information, to deliver asymptomaticelectrical stimulation through the electrode structure to the subject'sdiaphragm for the purpose of triggering the intended biphasic,caudal-followed-by-cranial, motion of the diaphragm.

A further modified form of the basic system of the invention,contemplated for implementation in certain applications, andrepresentationally pictured, described and included herein in each ofthe two principal embodiments disclosed, is one wherein the computerstructure which forms part of the included circuit structure possessestiming-adjustment substructure capable of making an adjustmentperiodically in the predetermined timed relationship which determineswhen, in relation to a sensed, valid V-event, electrical diaphragmaticstimulation occurs. This modification is versatile in its utility,offering the possibility of adjusting, either remotely, or internallyautomatically if desired, such stimulation timing in a manner aimed atfurther enhancing a subject's hemodynamic performance if, and as, thesubject's heart-behavior conditions change over time.

These and other systemic aspects of the invention, preferred andmodified, are discussed below herein.

From a methodologic point of view the invention offers a method forimproving the hemodynamic performance of a subject's heart including,from adjacent a selected surface region in the subject's diaphragm whichis out of contact with, the heart, (1) sensing and noting the presencesin the subject's cardiac cycles of a selected one of (a) per-cycle validelectrical, and (b) per-cycle valid mechanical, V-events, (2) based uponsuch sensing, and upon noting each of such selected, V-event presences,applying, in a predetermined timed relationship to such a noting,associated, asymptomatic electrical stimulation directly to thediaphragm, preferably at the selected diaphragmatic surface region, forthe purpose of triggering biphasic, caudal-followed-by-cranial motion ofthe diaphragm, (3) following the applying step, monitoring the waveformof resulting diaphragmatic motion, (4) after performing the monitoringstep, comparing the monitored diaphragmatic-motion waveform with areference, diaphragmatic-motion waveform, and (5) on completion of thecomparing step, recording the monitored, diaphragmatic-motion waveformfor later review.

The invention methodology further includes (1) choosing the selecteddiaphragmatic surface region to be on one of (a) the inferior, and (b)the superior, side of the diaphragm, and (2) choosing the selected,per-cycle valid V-event whereby, if it is to be electrical, it is one of(a) the R wave, and (b) the Q wave, and if mechanical, it is the S1heart sound.

These and various other features and advantages that are offered by thesystem and methodology of the present invention will become more fullyapparent as the detailed description of the invention which followsbelow is read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric, electrode-side, facial view of a fullyimplantable fully self-contained, self-powered, singular capsule-formembodiment of the system of the present invention.

FIG. 2 is a same-scale, lateral isometric view of the embodiment shownin FIG. 1, slightly rotated about two axes relative to what is seen inFIG. 1.

FIG. 3 is a plan view of the invention embodiment shown in FIGS. 1 and2, drawn on about the same scale used in these two figures, and picturedwith the body of the capsule in this embodiment opened to showinternally contained electrical circuitry, an accelerometer, and anincluded battery.

FIG. 4, which uses the same drawing scale as that seen in FIG. 3, is alateral cross section taken generally from the lower side of FIG. 3.

FIG. 5 is a basic block/schematic diagram illustrating electrical andmechanical componentry employed in the system of the invention andincorporated both in the invention embodiment pictured in FIGS. 1-4,inclusive, and in the still-to-be-mentioned, alternative embodimentshown in FIG. 8.

FIG. 6A is a frontal view of an internal portion of a subject's anatomyillustrating preferred, implanted positioning therein proposed for thesystem embodiment shown in FIGS. 1-4, inclusive.

FIG. 6B is similar to, and is drawn on about the same scale as thatemployed in, FIG. 6A, except that it shows an alternative placement inthe anatomy for the system of FIGS. 1-4, inclusive.

FIGS. 7A, 7B present enlarged-scale, fragmentary portions of theanatomical structure shown in FIGS. 6A, 6B, with the system of FIGS.1-4, inclusive, removed for clarity purposes, illustrating,specifically, biphasic mechanical movement, or motion, of the heartresulting from electrical stimulation, and resulting mechanical motion,of the diaphragm and heart in accordance with practice of themethodology of the present invention. FIG. 7A pictures a condition ofasymptomatic-stimulation-produced caudal diaphragmatic motion, and FIG.7B a condition of related, immediate-time-following, cranialdiaphragmatic motion.

The statements just made, which draw relationships between conditionspictured in FIGS. 7A, 7B, with respect to FIGS. 6A, 6B, respectively,are equally applicable to relationships that exist between FIGS. 7A, 7B,and still-to-be-described FIGS. 9A, 9B.

FIG. 8 illustrates an alternative, fully implantable systemic embodimentof the present invention—one which has a distributed structuralcharacteristic resulting from the condition that certain components inthis embodiment are arranged in two assemblies that are separated fromone another by an interconnecting communication lead structure.

FIGS. 9A, 9B are similar to FIGS. 6A, 6B, respectively, differing inthat they illustrate two, alternative, proposed internal anatomicalplacements for certain ones of the components included in the embodimentof the invention pictured in FIG. 8.

In FIGS. 6A, 6B, 9A and 9B, the exposed anatomical contents are greatlysimplified in order to avoid unnecessary complexity without compromisingdisclosure necessity, and in this context, lower portions of theleft-side phrenic nerve structure have been removed to afford betterviewing clearance to see the positioning illustrated therein forimplanted system structure.

The various structural and anatomical elements shown in FIGS. 1-7B,inclusive, and in FIGS. 9A and 9B, and the several moved anatomicalpositions, and changed anatomical configurations, pictured in FIGS. 7Aand 7B, are not necessarily drawn to scale.

FIGS. 10 and 11 present two, different, laddergram illustrationspicturing, respectively, what are referred to herein as earlydiaphragmatic, and late diaphragmatic, electrical stimulation.

FIG. 12 is a two-trace, common-time-base, graphical presentationrelating to electrical V-event sensing, associatedcardiac-cycle-synchronized, diaphragmatic stimulation, and resultingdiaphragmatic and left-ventricle biphasic mechanical motions.

FIG. 13 furnishes an enlarged view of a single cardio cycle eventpictured between a pair of spaced, vertical, short dashed lines in FIG.12.

FIG. 14 is a high-level, block/schematic diagram illustrating both thebasic, and one modified, form of the architecture of the methodology ofthe present invention.

DETAILED DESCRIPTION

Turning now to the drawings, and referring first of all to FIGS. 1-5,inclusive, indicated generally at 20 is one preferred form of aself-contained, self-powered, fully implantable medical systemconstructed in accordance with the present invention for improving thehemodynamic performance of a subject's heart. System 20 accomplishessuch improvement, as will be explained, through applying speciallytimed, cardiac-cycle-synchronized, asymptomatic, electrical stimulationdirectly to the subject's diaphragm to produce very short duration,relatively high-frequency (as mentioned above), bi-phasic motion of thediaphragm, which motion becomes communicated/applied directly to theunderside of the left ventricle in the heart to create, essentially, adiaphragmatic-motion-following, bi-phasic “pumping” motion in and forthe underside of, and thus within, the left-ventricle.

System 20, as seen in FIGS. 1-4, inclusive, has what is referred toherein as a singular capsule form 22. This form features a small, easilyimplantable, elongate, thin, non-electrically-conductive, andappropriately biocompatible capsule body, or capsule, 24 having theshape shown, with a length herein of about 1.25-inches, a width of about0.5-inches, and a thickness of about 0.125-inches. Body 24, has a hollowinterior 24 a (see FIGS. 3 and 4), and possesses an elongate, outside,diaphragm-contacting face 24 b (see FIGS. 1 and 2), also referred toherein as an electrode face, near the opposite ends of which arepositioned two, spaced (by about 1-inches), and outwardly exposed,bimodal electrodes 26, 28, referred to collectively herein as bimodalelectrode structure. Electrodes 26, 28 present exposed, circular faces26 a, 28 a, each having a diameter herein of about 0.15-inches.Generally speaking, these electrodes function, in an implanted-conditionoperation of system 20, both to sense heart-related electricalactivity—done in a so-called first, or one, mode of operation, and toapply controlled, asymptomatic, electrical stimulation to thediaphragm—done in a so-called second, or other, independent mode ofoperation.

The specific capsule shape illustrated in FIGS. 1-4, inclusive, and theseveral specific dimensions just mentioned, are not critical, and may bevaried selectively according user wishes to suit different, particularimplantation applications. What is important, of course, is that theshape and dimensions of capsule 24 be suitable and comfortable, anddesigned for minimally invasive placement for operational residencewithin a subject's anatomy. As will be explained below, while preferredplacement involves, effectively, stabilized attachment to a surfaceregion which is near the upper portion of a subject's diaphragm(inferior or superior), there may be other diaphragmatic locations thatare suitable for placement. The same statements just made about shapeand sizing, addressed initially specifically herein with respect to thecapsule form of the invention now being discussed, are also applicableto a still-to-be-described, second preferred embodiment pictured in FIG.8. Respecting each of the two, principal forms of the invented systemdisclosed herein, while users/installers of it may readily choosevarious, different, appropriate, and preferably minimally-invasive,surgical procedures to carry out implantation within a subject'sanatomy, laparoscopy is considered to be a good choice for systemplacement on the inferior side of the diaphragm, and thoracotomy, a goodchoice for such placement on the superior side of the diaphragm.

A suitable, conventional, non-electrically-conductive, biocompatiblemesh 30 (see FIGS. 1 and 2), is affixed to capsule face 24 b tofacilitate, following system implantation, natural-process anatomicalbonding, for positional stabilization, to a selected surface region(inferior or superior) in/on a subject's diaphragm. Inclusion of such amesh is optional, but useful. As will be further discussed, inferiorsurface-region placement on the diaphragm is preferred, and alsopreferably, though not necessarily, at a diaphragmatic location which isleft-lateral in a subject's anatomy. Additionally, under allcircumstances involving superior surface-region placement, suchplacement should be one where capsule 24 is out of direct contact withthe heart.

Included in system 20, housed within the hollow interior 24 a in capsulebody 24, are various electrical and mechanico-electrical,system-operational components, including an electrical circuit structure32 which, through the included presence in it of logic-including,internal-control circuitry (still to be pointed out in the drawings),manages all system electrical-performance activity, a battery 34 whichfurnishes all needed operating power for the system, and a multi-axial(three-dimensional herein) accelerometer, or mechanical sensingstructure, 36 which, with the system in an appropriate anatomicallyimplanted condition, senses a variety of mechanical and soundactivities, such as diaphragmatic-motion activities, and heart sounds.Regarding the accelerometer's sensing of diaphragmatic-motion activity,a sensing capability enhanced by its proposed, and intended, implantedplacement in what is referred to herein as a motion-sensing relationshipdirectly on the diaphragm, it produces an important electrical,diaphragmatic-motion confirmation signal for delivery to electricalcircuit structure 32, which signal is directly indicative of thewaveform of such motion. This signal is significantly useful forassuring that actually applied electrical diaphragmatic stimulation isas best-suited as possible for triggering the desired biphasicdiaphragmatic movement intended to maximize hemodynamic performanceenhancement. This assuring comes about because, according to themethodology of the present invention, the waveform represented by theaccelerometer's supplied confirmation signal is regularly compared witha reference waveform “known” to the system of the invention.

Heart sounds sensed by the included accelerometer are useful for manypurposes, and especially the S1 heart sound which is used, in an already(above) mentioned, modified form of the invention to act, and berecognized as, a valid mechanical V-event in relation to whichappropriate timing for the application of a diaphragmatic stimulation ismeasured.

Other interesting information which may be obtained, if desired, fromthe response of the system-included accelerometer, not directly relatedto the practice and methodology of the present invention, butnevertheless available, for example, to a physician monitoring varioussubject conditions that may, in different ways, have a relationship tohemodynamic performance, include subject activity levels, subject bodyposture, respiratory information, such as respiration rate,sleep-disordered breathing events, heart murmurs, and perhaps others.

An operative connection between circuit structure 32 and accelerometer36 is represented in FIG. 5 by conductors 36 a, 36 b.

Electrodes 26, 28 are operatively connected to circuit structure 32 forbimodal (sensing/stimulating) operation through what may be thought ofas bi-directionally employed conductors 26 b, 28 b, respectively, andthese electrodes, circuit structure 32, battery 34, and accelerometer 36are all appropriately operatively interconnected to functioncollaboratively in manners shortly to be described.

Appropriate, conventional, analogue-to-digital, and digital-to-analogueconverters, not specifically shown in the drawings, are incorporatedwhere needed.

Electrical circuit structure 32, as mentioned generally above, featureswhat is referred to as logic-including, internal-control circuitry, alsoreferred to herein as computer structure, or more simply as a computer,38, possessing waveform monitoring and recording substructure 40, andoptionally (representationally present herein), timing adjustmentsubstructure 42. Preferably, computer 38, which could, if desired, befully hard-wired to perform its intended functions, is hereinincorporated and configured with a microprocessor, or the like, so as tobe at least partially, if not fully, algorithmicallysoftware-programmable structure—programmable, in the system now beingdescribed, not only initially, but, if desired at later times, byclose-proximity telemetry communication accommodated through asystem-included, conventional, short-range radio 44 having an antenna 44a. Computer 38 also includes a suitable, conventionally designed “statemachine” (not specifically, separately illustrated in the drawings) forimplementing various important timing controls, as will be explainedbelow herein.

Choices for, and appropriate organizations of, specific electricalcircuitry elements, including logic-structure computer-associatedelements, and all hard-wired-managed, and/orsoftware-dictated-and-managed, operational “programming” which controlssystemic and methodologic functioning of the invention, are designableand includable employing conventional, state-of-the-art devices,algorithms, and other knowledge in the possessions of those persons whoare generally skilled in the relevant arts, and for that reason are notspecifically detailed herein. The systemic structural descriptionspresented herein, as well as the methodological, operational features ofthe invention discussed, will well arm those generally-skilled personsto practice all aspects of the present invention.

Turning attention now to FIGS. 6A, 6B, 7A, 7B, along with continuedreferences, as appropriate and helpful, to FIGS. 1-5, inclusive, FIG. 6Afurnishes, as stated earlier, a frontal view of an internal portion 46of a subject's anatomy illustrating, generally at 48, preferred,implanted positioning therein proposed for the system 20 pictured inFIGS. 1-4, inclusive. In FIG. 6A, system 20 is simply illustrated by avery evident, generally horizontally disposed, thickened, dark line, andspecifically, what is illustrated, is that capsule 24 in this system isplaced at a selected surface region 48 a on the inferior side of thesubject's diaphragm 50. More specifically, capsule 24 is positionedleft-laterally in the subject's anatomy, clearly out of contact with thesubject's heart 52, and actually in a modest state of compressionbetween the inferior side of diaphragm 50 and the subject's immediatelyunderlying liver, seen generally, and fragmentarily only, at 54. In avery specific sense, capsule 24 is disposed with its electrode face 24 b(not specifically seen or marked in FIG. 6A) facing the inferior surfaceof the diaphragm, with electrodes 26, 28 (also not specifically seen inthis figure) directly contacting diaphragmatic surface region 48 a.

In relation to what is seen in FIG. 6A, and as was mentioned earlierherein, capsule 24 has been implanted through conventional laparoscopy—asurgical practice which forms no part of the present invention.

Turning attention to FIG. 6B, this figure also shows just-mentioned,internal, anatomical portion 46, and is similar to FIG. 6A, except thatit shows an alternative placement in the subject's anatomy for capsule24 in system 20. In FIG. 6B, capsule 24 has been placed on the superiorsurface of diaphragm 50 at an implantation position generally shown at56, and specifically on a selected, diaphragmatic surface region 56 a,which has a left-lateral disposition in the subject's anatomy similar tothe left-lateral implantation disposition pictured on the underside ofdiaphragm 50 in FIG. 6A. Here, capsule 24 is disposed with its electrodeface 24 b (not specifically seen or marked) facing the superior surfaceof the diaphragm, and with electrodes 26, 28 (also not specificallyshown in FIG. 6B) directly in contact with the diaphragm.

In the disposition shown in FIG. 6B for capsule 24, the capsule isslightly compressed between the superior surface of diaphragm 50 and theunderside of the subject's left lung 58.

In relation to the positioning shown for capsule 24 in FIG. 6B, and aswas mentioned earlier herein, this capsule has been implanted throughconventional thoracotomy—another surgical procedure which also forms nopart of the present invention.

Turning attention now to FIGS. 8, 9A, 9B, indicated generally at 60 inthese three figures, and focusing attention initially here on what isshown in the FIG. 8, is the second. above-mentioned, principal form ofthe invention, which is a self-powered, implantable, distributed form ofthe invention—distributed in the sense that it includes a pair of spacedcomponent assemblies 62, 64, operatively interconnected by appropriate,elongate, communication lead structure 66. Except for the fact that thisform of the invention has the just-mentioned distributed nature, and thefurther fact that it's distributed componentry, when implanted in asubject's anatomy as pictured generally in FIGS. 9A, 9B is uniquelyassociated with this distributed embodiment form, it includes all of theoperatively interconnected electrical and mechanico-electricalcomponentry described above for system form 20—interconnected asillustrated schematically in FIG. 5. Additionally, the performance ofsystem 60 is essentially identical to that of system 20.

Included within component assembly 62 are a cylindrical housing 68, fromone side of which projects a spiral-form, diaphragm-attaching electrode70, and in which is appropriately mounted a three-dimensionalaccelerometer 72 represented by a small thickened and darkened line inFIG. 8, and next to housing 68, and represented by a small rectangle,another electrode 74 which, together with electrode 70, form thepreviously mentioned bimodal electrodes. Collectively, electrodes 70, 74constitute the bimodal electrodes structure discussed above.

Shown immediately to the right of component assembly 62 in FIG. 8, andvisually linked to the image of this component assembly by a curved,double-arrow-headed arrow 76, is a symbolic representation 78 ofassembly 62, which symbolic representation is employed (as can be seen)in each of FIGS. 9A, 9B to enable a simpler way of picturing there therespective presences of assembly 62 in the anatomical images presentedin these two figures.

Electrode 70, the spiral-form electrode, is designed to enable spiral,attachable embedment into the structure of a subject's diaphragm forsecuring component assembly 62 in place, and in a manner whereby bothelectrodes 70, 74 will essentially be in contact with a selected surfaceregion in the diaphragm, with accelerometer 72 in an appropriatemotion-sensing relationship relative to, and effectively in contactwith, the diaphragm.

Lead structure 66 includes conductors (not illustrated in specificdetail) which are appropriately connected to electrodes 70, 74, and toaccelerometer 72, which conductors extend in the lead structure tocomponent assembly 64.

Component assembly 64 includes all of the system electrical circuitry,the system battery, and the system radio and antenna (not specificallypictured in FIG. 8), such as those, same elements illustrated in FIG. 5.The length of lead structure 66 is a matter of user choice, and willtypically be chosen, of course, to accommodate intended implantationdisposition of system 60 within a particular subject's anatomy.

Focusing now on FIGS. 9A and 9B, and beginning with what is shown inFIG. 9A, here, one can see that system 60, as was true for theillustration provided in FIG. 6A for system 20, is disposed atpreviously mentioned implantation position 48 on also previouslymentioned inferior diaphragmatic surface region 50 a. One will note thatonly, within system 60, component assembly 62 is shown in FIG. 9A, withlead structure 66 broken away, and component assembly 64 notspecifically pictured. A reason for this is that what is important tonote with respect to what is seen in FIG. 9A is the diaphragmaticpositioning of component assembly 62, with one recognizing thatimplantation of the other end of system 60, namely, component assembly64, can be located at the user's choice, and suitably, anywhere in thesubject's anatomy below diaphragm 50.

FIG. 9B, which, as has already been mentioned, is very similar to FIG.6B, shows system 60 disposed at previously mentioned implantationposition 56 on also previously mentioned diaphragmatic surface region 50b, located on the superior side of diaphragm 50.

Here, too, lead structure 66 is broken off with component assembly 64omitted from FIG. 9B, one here recognizing that the installer of system60 will choose an appropriate, above-the-diaphragm placement site forcomponent assembly 64.

Addressing attention now, briefly, to the implantation dispositionsshown in FIGS. 6A, 6B, and 9A, 9B, for systems 20, 60, respectively,which dispositions, are left-lateral in the subject's anatomy, andeither inferior (preferred) or superior relative to the diaphragm, ineach of these dispositions the electrodes and the accelerometers areessentially in direct contact with the described and illustrated surfaceregions in the diaphragm, out of direct contact with the heart.Additionally, in each of the system dispositions shown in these fourfigures, the electrodes in the respective systems are well positioned todetect easily heart-associated electrical activity, and theaccelerometers are similarly positioned to detect easily heart sounds,and, of course, diaphragmatic movement/motion.

Having now completed descriptions of what is illustrated in FIGS. 6A,6B, 9A, 9B, I to turn attention to FIGS. 7A and 7B. As a reminder, andas was pointed out in the text above regarding the descriptions of thedrawings, in each of FIGS. 7A, 7B, system components of the inventionhave been omitted so that one can more easily focus on themotion-created nature of, and behaviors associated with, diaphragmaticelectrical stimulation produced by operations of the systems of theinvention. In each of these two figures, and recognizing that theypresent enlarged, and very small fragmentary regions drawn from theanatomical presentations seen in FIGS. 6A, 6B and 9A, 9B, the anatomicalleft side of diaphragm 50 is shown in solid outline in a non-stimulatedcondition relative to the adjacent anatomical components, andparticularly relative to heart 52 and its left ventricle.

As indicated by a downwardly-pointing arrow 80 in FIG. 7A, on theinitiation of an electrical stimulating pulse applied to diaphragm 50,the diaphragm moves downwardly rapidly in a caudal direction to aposition which is somewhat exaggeratedly illustrated for it in dashedlines at 50A in this figure. This caudal movement of the diaphragm,because of the diaphragm's intimate association with the base of theleft ventricle in heart 52, pulls downwardly on this ventricle toproduce the position for the lower part of the heart and ventricle shownin dashed lines at 52A in FIG. 7A.

FIG. 7B pictures relevant, moved relationships which exist immediatelyfollowing the conditions shown in FIG. 7A. More specifically, anupwardly pointing arrow 82 in FIG. 7B shows conditions wherein diaphragm50 has moved upwardly in a cranial direction to the exaggerated, movedposition for it shown in dashed lines at 50B—a diaphragmatic movementwhich drives upwardly on the underside of the left ventricle in theheart to create a heart and left ventricle moved condition pictured indashed lines at 52B.

The time-sequential moved conditions pictured in FIGS. 7A, 7B, are,essentially, repeated synchronously in each cardiac cycle of a subject'sheart in accordance with what constitutes herein predetermined timingassociated with, and triggered by, the sensed occurrence of a valid,electrical or mechanical V-event, sensed either electrically by thebimodal electrode structure functioning in its “one”, sensing mode asestablished for it by operatively connected electrical circuit structure32, or mechanically by the included system accelerometer. As will beexplained shortly, with the system of the invention implanted andoperating in a subject's anatomy, and set to “look for”, and employ, forexample, valid electrical V-events as “triggers” for implementing acardiac-cycle-synchronized, shortly-to-follow diaphragmatic stimulation,cardiac-cycle-synchronized, stimulation-produced diaphragmaticmovements, biphasic in nature as described above, occur in every cardiaccycle, except in what may be referred to as a non-normal cardiac cyclein which there occurs, unexpectedly, an electrical V-event which “lookslike”, but is not, an appropriate, valid, electrical V-event thatpresents itself during that cardiac cycle's associated refractoryperiod. More will be said about this special circumstance shortly inrelation to what is shown in FIG. 10. The occurrence of such a non-validelectrical V-event within a cardiac cycle's refractory period creates asituation where, in order to protect against lack of efficiency andpotential difficulty, no related, next-following electrical stimulationis applied to the diaphragm.

FIGS. 10 and 11, as mentioned earlier, present conventional-styleladdergrams which picture, respectively, what are referred to herein as(a) early, or anticipatory, diaphragmatic stimulation (PIDS), and (b)late, or following, diaphragmatic stimulation (PIDS). As just indicatedin the preceding sentence, in discussions now following regarding thesetwo drawing figures, as well as in still-to-be-presented discussionsrespecting FIGS. 12 and 13, the previously identified term PIDS will, attimes, be used, in the text (and in the illustrating drawings) toidentify diaphragmatic stimulation.

As a preliminary orientation to the manners in which FIGS. 10 and 11 aredrawn, each figure includes a pair of vertically spaced, horizontal timelines, labeled “V” and “P”, where V stands for a V-event, and P stands,in a shortened manner, for the acronym PIDS (electrical diaphragmaticstimulation). The time lines in these two drawing figures effectivelycover four, representative cardiac cycles, and each figure includes, atits lower left side, a self-explanatory, graphical-symbol legend whichis associated with the several, and various, graphical indicia that aredistributed along the time lines above in the figure.

Except for the specific discussions now to follow which explain certain,important predetermined timing settings pictured in thesedrawings—settings that relate to notable operations of the system of theinvention, I believe that those who are generally skilled in therelevant art will clearly understand the information conveyed by therelated sequences of events pictured in these two drawing figures,especially in the context of understanding that operation of the systemof the present invention involves cardiac-cycle-synchronized sensing ofvalid V-events, electrical or mechanical, and the using of such sensedand noted events as triggers for the implementation of a then-following,electrical diaphragmatic stimulation.

Having said this, it should be evident that the upper time line in eachof these two drawings pictures, among other things, a sequential seriesof sensed V-events, and that the lower time line represents respectivelyassociated, thereafter-following PIDS stimulations. Angular, slopingdashed lines which extend in each of FIGS. 10 and 11 downwardly and tothe right between the upper and lower time lines relate to what arereferred to herein as V-PIDS timing periods or delays, and also aspredetermined timed relationships—parameters that are functional in theoperation of the system of the invention in accordance either with (a)user-selected presetting of these delays, (b) used re-setting of thesedelays after a period of system operation, and/or (c) on-the-fly,system-internal, systemically self-effected adjustments of such delays,where such system-internal adjustments are permitted (i.e.,user-selectively accommodated by appropriately system-included,conventional logic programming). In all embodiments of the system of theinvention that are currently contemplated, adjustments in the V-PIDSdelay parameter, both in a necessary pre-setting manner with the systemin an implanted (or not) condition, and later, if desired, in asystem-implanted re-setting situation, are permitted via remotetelemetry, or otherwise. The graphically illustrated V-PIDS delays“represented” by the sloping, dashed lines in FIGS. 10 and 11, areactually measurable, i.e. visualizable, graphically in these figures ina manner and direction which is horizontally parallel to the time lines,and not angularly.

Saying a little bit more in an orientation sense regarding FIGS. 10 and11, the relational, sensed V-events and associated stimulationoccurrences pictured may now be thought of as being presented, forfurther and discussion illustration purposes herein, in the context ofan implementation of the invention wherein it is valid, electricalV-events have been selected to be the markers, i.e., the triggers, forPIDS stimulation.

Continuing with description relating to matters shown graphically inFIGS. 10 and 11, there are two, important, and importantly related,timing periods that are taken into account in the practice of thepresent invention, one of which, the V-PIDS delay period, has just beendiscussed, and the other of which is the length of the so-calledrefractory period that exists in each of a subject's cardiac cycles,immediately following a sensed, valid V-event in that cycle. In thesetwo figures, the relevant refractory periods are represented graphicallyby elongate, vertically-thin, horizontal rectangles distributed alongthe time lines. The graphical legends presented in FIGS. 10 and 11 makeclear which illustrated “rectangles” these are.

Timing operations, with respect to these two time periods are under thecontrol of two, logic-based timers that are realized/implemented, and“operated”, so-to-speak, in appropriate timing-tracking manners by thepreviously-mentioned, included-logic state machine in its associationwith the electrical-circuitry-included logic, or computer, structure.

The time-period associated with the timer which deals with tracking acardiac-cycle refractory period, a period which, as was just mentioned,begins immediately following the sensing of a chosen, valid V-event,involves subject-specific data that is pre-known, for example, to amedical practitioner using the system of the invention, and who isfamiliar with the particular subject to be equipped with the system. Fora given subject, and as a precursor typically to implantation, andcertainly to activation, of the system of the present invention withrespect to that subject, two pieces of subject-specific information arerelevant to establishing what will be, at least initially, a presetduration for a timed refractory period. Required for this determinationare (1) knowledge of the expected likely heart-rate range of thesubject, and (2) knowledge regarding the specifically chosen event(electrical in the situation now being discussed) in each of thesubject's cardiac cycles which will be treated as the valid V-event fromwhich a measured time will be observed to determine the application of afollowing, diaphragmatic stimulation. In the description now underwaywith respect to FIGS. 10 and 11, and, in fact, in the operationaldescription of the system and methodology of the invention still tocome, all operational behavior will be described, for illustrationpurposes, in the setting of a pre-selection having been made for thedetected onset of the electrical R wave in each cardiac cycle being thevalid, triggering V-event. A conventional, appropriately programmed,EGC-watching approach is used herein to detect this onset in relation toECG electrical information regularly sensed by the system bimodalelectrode structure functioning in its “one”, sensing mode under thecontrol of the system electrical circuit structure.

Of the two, alternative V-PIDS delay-time possibilities contemplated forpractice of the present invention, I have found that, in mostapplications, so-called early PIDS stimulation is preferable, and it isfor this reason that FIG. 10, in the two-drawing-figure,pictorial-numeric sequence which has been selected for the presentationsin the drawings of FIGS. 10 and 11, has been chosen to illustrate suchstimulation. Early PIDS stimulation, and the relevant V-PIDS time delayassociated with it, lead effectively to a condition for the applicationof diaphragmatic stimulation at the beginning of a short time intervalwhich lies, in time, as a precursor to the onset of an anticipatedV-event in a particular cardiac cycle (to be explained). In a manner ofthinking, therefore, one can imagine that the actual (precursor) timegap existing between such early PIDS stimulation and the shortlyfollowing onset of a valid, “anticipated”, and soon to be next-sensed,valid V-event constitutes a negative time interval in the cardiac cyclewhere stimulation is to take place. Because of this, and because suchstimulation must be measured from an already-having-occurred, sensedvalid V-event, the system and methodology of the present inventionperform this measurement beginning from the just previously sensed,valid V-event in the immediately prior cardiac cycle.

Continuing with this thought, and recognizing that proper establishment,for successful systemic operation, in an early-PIDS manner offunctioning, of an appropriate a V-PIDS delay interval following theoccurrence of the sensed V-event which is employed to triggerstimulation action, it is important to know, and this is done by anaveraging technique, just how to anticipate a next-expected validV-event. To this end, and employing conventional algorithmic programmingwell-known to those generally skilled in the relevant art, once thesystem of the invention has begun its operation, and after the first fewcardiac cycles associated with that operation, a running average isperformed based (in the present system implementation) upon the four,prior cardiac cycles to assess an average timing expected betweensuccessive, valid V-events. This average is “made known” within thelogic componentry in the system for every successive cardiac cycle afterthe first four cycles which mark the beginning of system operation, andaccordingly, on-the-fly, so-to-speak, a V-PIDS timing delay,“represented” in FIG. 10 by the previously-mentioned, sloping dashedlines, is calculated by performing, effectively, a subtraction, from thethen-available averaged timing determined between successive, validV-events, of the brief, precursor interval (just mentioned above) thebeginning of which is intended to define the moment of triggering of aPIDS stimulation in anticipation of the expected, very shortlyfollowing, next-valid, and sensed, V-event.

If desired, the system of the present invention may be structured in aconventional manner to allow the making of a change associated withearly PIDS stimulation through the making of a change in settingsavailable to the system describing, differently, the short precursor(subtraction anticipatory) interval just discussed.

Continuing with the discussion regarding what is shown in FIG. 10, thisfigure illustrates the potential problem-creating possibility (mentionedearlier) of an errant V-event which occurs, outside of normal cardiacbehavior, within a particular cardiac cycle's refractory period. Lookingspecifically toward the right side of what is shown in FIG. 10, seenalong the upper time line is a presentation of the occurrence of such anerrant V-event which has taken place during the illustrated cycle'srefractory period. To the right of this indication in the upper timeline, and specifically below the associated, lower time line, text ispresented indicating that there is not to be animmediately-next-following PIDS stimulation—a protective measure, asnoted earlier.

Directing attention now to FIG. 11, and as a reminder about the natureof the teaching which is evident in this figure, FIG. 11 describes whathas been referred to as a late PIDS stimulation situation. Thissituation is very easy to understand, in the sense that to implement it,all that is required is a system setting for a predetermined V-PIDSdelay time which is very short, typically, and which, within a commoncardiac cycle, shortly follows a sensed, valid V-event.

In relation to a final point to mention regarding FIGS. 10 and 11, smallblackened rectangles distributed, as shown, along the V time lines inthese figures mark short, conventionally-system-implemented blankingperiods that are created and exist to prevent a stimulation pulse fromproducing unintended cardiac electrical activity. In the early PIDSsituation, these blanking periods fall outside of the cardiac-cyclerefractory periods. In the late PISD situation, they occur duringrefractory periods.

Turning attention now to FIGS. 12 and 13, FIG. 12 illustrates, alongtwo, vertically spaced, time-related time lines, (1) an upper graphicaltrace of an ECG waveform received from subject-implanted systemelectrodes, picturing a large plurality of successive subject cardiaccycles, including the evident presences of cycle-synchronized PIDSstimulations, and (2) a lower graphical trace of related outputinformation received from the implanted-system-included accelerometershowing both the lower-frequency characteristic of normal respiration,and the superimposed, higher-frequency, cardiac-cycle-synchronized,biphasic diaphragmatic motions that have resulted from the PIDSstimulations shown above in the electrically illustrated cardiac cycles.The waveforms of these biphasic diaphragmatic motions, captured andrecorded, as they are, for later reporting by the system of the presentinvention, are importantly useful for helping a medical professional, inthe setting of actually seeing the waveform of what biphasic,diaphragmatic, stimulation-produced motion looks like, to assess both,ultimately, the quality of a subject's hemodynamic performance, and alsothe quality of enhancement-assistance thereof furnished by theinvention.

FIG. 13 furnishes an enlarged, and time-stretched, view of fragments ofthe two traces presented in FIG. 12, selected from the region in FIG. 12marked by the two, vertical, laterally-spaced dashed lines that mark adisplay region for FIG. 13 designated 84 in FIG. 12.

What can be seen by looking at these two drawing figures, very clearly,is that each illustrated PIDS stimulation, which is short-term andpulse-like in nature, produces, in the represented subject's diaphragm'smovement, a related, cardiac-cycle-synchronized, relatively highfrequency, biphasic, caudal-followed-by-cranial movement of thediaphragm. It is this relatively high-frequency, biphasic, diaphragmaticmotion, caudal-followed-by-cranial in nature, which, in the context ofthere being a properly waveform-shaped motion of the diaphragm, enhancesa subject's hemodynamic performance through the effective delivery ofthat diaphragmatic motion to the underside of the heart's leftventricle, as explained earlier.

As was mentioned earlier herein, internal programming, hard-wired and/oralgorithmically programmed/programmable, is in many ways completelyconventional in nature in terms of specific tasks that are performableduring operation of the system of the present invention. While, as hasalready been mentioned above, there are certain settings that,preferably, are introduced as initial settings introduced to thecircuitry logic structure provided in the system of the invention—putthere into place by the system user/installer/implanter—there arecertain operational features and re-settings which may, over time, beadjusted and/or introduced, either remotely through short-rangetelemetry accommodated by radio 44, or automatically internally inassociation with a systemic capability, if such a capability isselectively provided, for the system to self-monitor and self-adjustvarious aspects of its own activities. With regard totelemetry-implemented operational modifications, as well as potentiallyinternally self-implemented operational modifications, again, thosegenerally skilled in the relevant arts will know how to do this basedupon the systemic and methodologic descriptions of the inventionpresented in this text and pictured in the associated drawing figures.

Regarding such potential modifications, and various associatedactivities, I recognize to be a very interesting category ofeasily-accomplishable self-modification, the making of changes in theabove-identified and discussed V-PIDS time-delay settings. As was alsopointed out earlier herein, importantly, with respect toself-implemented operational modifications, the system and methodologyof the present invention do not allow for the self-implemented making ofany changes in the character of electrical diaphragmatic stimulation. Itis, of course, entirely possible for a system user who is monitoring asubject's hemodynamic performance condition, to make such modificationsremotely by telemetry.

An important and special feature of the present invention involves thecapturing and recording of accelerometer data associated with the natureof actual, stimulation-produced diaphragmatic biphasic movement. Thiscapture and recording, in association with an importantly implemented,and uniquely contemplated, comparison of captured, actual diaphragmaticmotion waveforms with a system-stored, carefully chosen, referencewaveform, yields reportable information that allows a system user toinitiate stimulation adjustments to improve matters. This comparisonactivity produces system-stored comparison data which is retrievable bytelemetry to furnish valuable confirmatory evidence of the viability ofthe implemented diaphragmatic stimulation respecting the maximizing andachieving of hemodynamic performance.

Before describing a typical operation of the system with respect to aparticular subject, let us turn attention to FIG. 14 in the drawingswhich illustrates, in block/schematic form, both the basic, and amodified, form of the architecture of the methodology of the presentinvention. The “overall” archaeology, as shown in FIG. 14, isillustrated generally at 86. It includes, as steps represented in blockform, six different blocks, including block 88 (Sensing), block 90(Applying), block 92 (Monitoring), block 94 (Comparing), block 96(Recording), and block 98 (Choosing). Blocks 88-96, inclusive, are drawneach with a solid-line outline to signify that they describe,effectively, the basic, or core, methodology of the invention. Block 98,which is outlined with a dashed line, represents one modified form ofthe invented methodology. Reading from left to right in FIG. 14, theseveral blocks there pictured are connected in the order of associatedbehaviors, with arrow-headed, right-pointing lines connecting theseblocks, as shown, to symbolize, the flow of methodologic activity.

The present invention thus offers a method for improving the hemodynamicperformance of a subject's heart including, from adjacent a selectedsurface region in the subject's diaphragm which is out of contact withthe heart, (1) Sensing and noting (Block 88) the presences in thesubject's cardiac cycles of a selected one of (a) per-cycle validelectrical, and (b) per-cycle valid mechanical, V-events, (2) based uponsuch sensing, and upon noting each of such selected, V-event presences,Applying (Block 90), in a predetermined timed relationship to such anoting, associated, asymptomatic electrical stimulation directly to thediaphragm, preferably at the selected diaphragmatic surface region, forthe purpose of triggering biphasic, caudal-followed-by-cranial motion ofthe diaphragm, (3) following the applying step, Monitoring (Block 92)the waveform of resulting diaphragmatic motion, (4) after performing themonitoring step, Comparing (Block 94) the monitored diaphragmatic-motionwaveform with a reference, diaphragmatic-motion waveform, and (5) oncompletion of the comparing step, Recording (Block 96) the monitored,diaphragmatic-motion waveform for later review.

The invention methodology, in a modified form, further includes (1)Choosing (Block 98) the selected diaphragmatic surface region to be onone of (a) the inferior, and (b) the superior, side of the diaphragm,and (2) choosing the selected, per-cycle valid V-event whereby, if it isto be electrical, it is one of (a) the R wave, and (b) the Q wave, andif mechanical, it is the S1 heart sound.

Presenting now a description of typical system preparation,implantation, and operation with respect to a particular, selectedsubject, this description will be based upon the implantation in asubject of that form of the system of the invention which is pictured inFIGS. 1-5, inclusive, and installed as illustrated in FIG. 6A. Further,this description will be based upon a predetermination that thetriggering of diaphragmatic stimulation will be based upon the sensing,in the subject's cardiac cycles, of valid electrical V-events, with thechosen, valid electrical V-event being the onset of the R wave. Theoperational description which now follows will also rest upon apre-decision that early PIDS stimulation is what is to take place, andthat until, as will shortly be described, a more concrete idea isreached for defining an exact V-PIDS delay interval, the system logicstructure—effectively, the state machine portion of this structure—willbe “told” to begin with a V-PIDS delay time of zero.

Also initially determined, and this, before system implantation, is whatkind of a timing interval to pre-assign to the refractory period timeroperated by the state machine, and this timing interval will be basedupon subject-specific information drawn from pre-knowledge about thesubject's expected likely heart-rate range, and typical refractoryperiod time length beginning with the onset of the R wave, and endingwith the end of that refractory period.

Also completely predetermined will be system settings that establish,essentially fixedly, the character of electrical PIDS stimulationdesigned to be clearly asymptomatic in nature.

Much of this pre-implantation information, relevant to preparing thesystem of the invention for best-possible work with the selectedsubject, will involve a further category of information, known to theappropriate medical personnel, regarding how to assess, with the systemoperating, maximally-achievable, enhanced hemodynamic performance.

With system pre-settings based upon the just-described preliminarychoices made, the system is implanted appropriately, as illustrated inFIG. 6A, and is switched into operation, with the system userimmediately collecting appropriate data to assess needed adjustment,from zero, to establish in the state machine the most appropriateearly-PIDS time interval now to be “reset” for per-cycle calculation ofthe important V-PIDS delay period. Those persons skilled in the medicalarts will know well how to make this assessment, and with this knowledgein hand, will, through short-range telemetry, introduce into the logicalstructure of the state machine, as just mentioned, the appropriateV-PIDS delay information.

With the early PIDS, V-PIDS delay period thus set, the system of theinvention now simply regularly estimates, through the on-the-flyaveraging technique described above, a proper point in time, followingthe sensing in one cardiac cycle of a valid electrical V-event, to applydiaphragmatic stimulation in the following cardiac cycle appropriately,and shortly, before the next-sensed, valid electrical V-event. Errantelectrical V-events sensed during a cardiac cycle's refractory periodwill not be used to trigger stimulation. Valid electrical V-eventsensing will take place through the system-included, bimodal electrodestructure placed by the system electrical circuit structure in its“one”, sensing mode, and electrical stimulation delivered to thediaphragm, under the controlling influence of the system electricalcircuit structure, will be delivered by the same, efficiently employed,bimodal electrode operating in its “other”, stimulating mode.Interesting to note here, specifically, is that the incorporation in thesystem of the present invention of the described, bimodal electrodestructure offers the simplicity of utilizing simply one pair ofelectrodes to perform, seriatim, electrical-activity sensing, andelectrical diaphragmatic stimulation.

Each sensed, valid electrical V-event will result in asymptomaticelectrical stimulation of the subject's diaphragm to producehigh-frequency, biphasic, caudal-followed-by-cranial diaphragmaticmovement, and this cycle-by-cycle activity will synchronously drive theleft ventricle of the subject's heart in a biphasic, pumping-assistmanner which will enhance hemodynamic performance as described above.

The system accelerometer will accurately follow the stimulation-inducedbiphasic diaphragmatic movement which is associated with eachdiaphragmatic stimulation, and will, cycle-by-cycle, communicate to theelectrical circuit structure the mentioned, related,diaphragmatic-motion confirmation signal whose associated waveform willbe compared with that of the mentioned, carefully-chosen referencewaveform to generate, for storage and later retrieval,cardiac-cycle-by-cardiac-cycle waveform comparison data.

All of this activity will be occurring, as mentioned, entirelysynchronously with the subject's cardiac-cycle-by-cardiac-cycle heartrate.

The operational description just presented, wherein the preselected,valid V-event has been chosen to be electrical and to be associatedspecifically with the detected onset of a cardiac cycle R wave, closelyalso describes both (a) an alternative system operation based uponselection of the Q wave as being the valid electrical V-event, and (b)another, alternative system operation based, instead, on mechanicalV-event sensing, wherein a selected, valid mechanical V-event is chosento be the S1 heart sound—an event which will be sensed by thesystem-included accelerometer. In this latter, alternative operationalsetting, the accelerometer plays the dual roles of sensing validV-events, and tracking and reporting on stimulation-produceddiaphragmatic movements.

Accordingly, while two, important, principal, systemic embodiments ofthe invention have been illustrated and described herein in detail, andcertain modifications suggested, and while, also, preferred and modifiedforms of system-implemented methodology and system operation have beendiscussed and illustrated, I recognize that other variations andmodifications may come to the minds of those generally skilled in therelevant arts, are possible, and may be made without departing from thespirit of the invention, and it is my intention that the followingclaims to invention will all be interpreted to have scopes which willembrace such other variations and modifications.

What is claimed is:
 1. An implantable medical system comprising: aplurality of electrodes for sensing electrical cardiac activity throughthe diaphragm and delivering electrical stimulation to the diaphragm;and a circuit structure coupled to the plurality of electrodes andconfigured to: obtain sensed cardiac activity corresponding to sensedelectrical cardiac activity, detect a cardiac event in a cardiac cyclebased on the sensed cardiac activity, and apply an electricalstimulation to at least one of the plurality of electrodes in a timedrelationship relative to the detected cardiac event.
 2. The implantablemedical system of claim 1, wherein the cardiac event corresponds to oneof a R wave and a Q wave.
 3. The implantable medical system of claim 1,wherein the electrical stimulation comprises a single pulse configuredto induce a singular asymptomatic motion of the diaphragm.
 4. Theimplantable medical system of claim 3, wherein the single pulse has aduration less than a cardiac cycle.
 5. The implantable medical system ofclaim 3, wherein the singular asymptomatic motion of the diaphragm ischaracterized by biphasic, caudal-followed-by-cranial motion.
 6. Theimplantable medical system of claim 3, wherein the asymptomatic motionof the diaphragm has a duration of a few tens of milliseconds.
 7. Theimplantable medical system of claim 1, wherein the timed relationship isone that: (a) anticipates a next-expected occurrence of the cardiacevent, or (b) follows a last sensed occurrence of the cardiac event. 8.The implantable medical system of claim 1, comprising a lead and ahousing, wherein: the plurality of electrodes are associated with thelead, the circuit structure is associated with the housing, and the leadand the housing are configured to couple together to thereby couple thecircuit structure to the plurality of electrodes.
 9. The implantablemedical system of claim 8, wherein the plurality of electrodes areconfigured to be coupled to one of an inferior side of the diaphragm,and a superior side of the diaphragm.
 10. The implantable medical systemof claim 1, comprising a capsule structure, wherein the plurality ofelectrodes and the circuit structure are associated with the capsulestructure.
 11. The implantable medical system of claim 10, wherein thecapsule structure is configured to be coupled to one of an inferior sideof the diaphragm, and a superior side of the diaphragm.
 12. A method forimproving hemodynamic performance of a heart through electricalstimulation of a diaphragm, the method comprising: obtaining sensedcardiac activity corresponding to electrical cardiac activity sensedthrough the diaphragm, detecting a cardiac event in a cardiac cyclebased on the sensed cardiac activity, and applying an electricalstimulation to the diaphragm in a timed relationship relative to thedetected cardiac event.
 13. The method of claim 12, wherein electricalcardiac activity is sensed through the diaphragm by a plurality ofelectrodes adjacent to or in direct contact with the diaphragm.
 14. Themethod of claim 12, wherein electrical stimulation is applied to thediaphragm through at least one of a plurality of electrodes adjacent toor in direct contact with the diaphragm.
 15. The method of claim 12,wherein the cardiac event corresponds to one of a R wave and a Q wave.16. The method of claim 12, wherein the electrical stimulation comprisesa single pulse configured to induce a singular asymptomatic motion ofthe diaphragm.
 17. The method of claim 16, wherein the single pulse hasa duration less than a cardiac cycle.
 18. The method of claim 16,wherein the singular asymptomatic motion of the diaphragm ischaracterized by biphasic, caudal-followed-by-cranial motion.
 19. Themethod of claim 16, wherein the asymptomatic motion of the diaphragm hasa duration of a few tens of milliseconds.
 20. The method of claim 12,wherein the timed relationship is one that: (a) anticipates anext-expected occurrence of the cardiac event, or (b) follows a lastsensed occurrence of the cardiac event.